What is the max usable size of the literal string identified by a helpKey constant?

Has anyone verified this?

In the following example (which I found in the Eclipse documentation topic for the "helpKey Constants Interface Class") what is the maximum usable size of the literal string "CONTEXT_ID_CP_PROPERTY_PAGE"?

In some older versions of Eclipse, you could define long IDs such as "CONTEXT_ID_CP_PROPERTY_PAGE" but the runtime would use only the first 10 characters or so. The result was that IDs that were different after 10 characters were treated as the same ID by the runtime.

Does this limitation still exist?

[Note: The "helpKey Constants Interface Class" documentation states that "the only characters allowed in a helpKey constant string are: upper case and lower case letters (a-z, A-Z), numbers (0-9), and the underscore (_)". There is nothing said about length.]